1. Field of the Invention
The present invention relates to a pattern shape inspection method and an apparatus thereof, capable of inspecting a shape of a line pattern on a magnetic recording medium formed of a patterned medium, especially, an inspection object, for example, a discrete track medium, a stamper thereof, or a master as a mold of the stamper as well as a pattern edge state at high speeds with high sensitivity.
2. Description of the Related Art
Recently, a mobile device and AV equipment for digital recording have been rapidly proliferating in addition to the PC and server, and the demand for the use of hard disk drive (HDD) has been growing. Amounts of information processed by the HDD have also been dramatically increasing. Meanwhile, the HDD has been demanded to be compact to increase the recording density of the magnetic recording medium. The perpendicular magnetic recording process has been developed accompanied with the increase in the recording density of the HDD. With the perpendicular magnetic recording process, the influence caused by the magnetic interference between adjacent tracks becomes greater as the recording density is increased, thus reaching the limit. As the process for recording/replaying only the subject track, discrete track media have been developed for physically processing the track so as to be magnetically decomposed. Bit patterned media for recording a single bit on a single magnetic particle have also been under development for a further increase of the recording density.
Unlike the generally employed magnetic recording medium, the discrete track media and the bit patterned media require formation of a track pattern or a bit pattern. The size of the track pattern or the bit pattern is as fine as several tens nm. The optical nano imprinting technique is employed as the method for manufacturing the fine pattern at low costs.
Variation in the size or shape, deficiency and short-circuit of the pattern formed by the optical nano imprinting may cause operating failure, resulting in defect. It is therefore essential to inspect with respect to adequate formation of the pattern shape. The defect of the stamper as the pattern mold, if any, will be copied, and accordingly, the highly accurate inspection is required. In the case of the defect caused in the course of the manufacturing process, the pattern shape or the pattern state has to be inspected in detail for identifying the cause of the defect.
SEM (Scanning Electron Microscope) and AFM (Atomic Force Microscope) are well known for inspecting the defect of the fine pattern. However, they may be applied to the inspection only for the limited region in view of the throughput.
Meanwhile, an optical surface inspection device and an OCD (Optical Critical Dimension) measurement device are known as the device for detecting the fine defect and the pattern shape defect with the high throughput. U.S. Pat. No. 7,233,390 discloses the method for measuring the line pattern using the scatterometory as the generally employed OCD measurement device when roughness exists on the semiconductor pattern edge.